The present invention relates to methods and catalysts for producing alkenes from alkanes. More particularly, the present invention relates to regenerable, encapsulated metal oxide catalysts and cost-effective processes utilizing such catalysts to convert alkanes to alcohols then to alkenes.
Lower alkenes, such as ethylene, propylene, and butylene, are used for a variety of applications. For example, ethylene is one of the most produced organic compounds in the world, with the majority of ethylene being used to produce ethylene oxide, ethylene dichloride, and polyethylene. Lower alkenes may be recovered from petroleum by fractional distillation, however, demand far exceeds recovery by this method. Therefore, the majority of lower alkenes are produced by energy intensive and expensive cracking processes that are well-known in the art. For example, ethylene is commonly produced at about 700-950° C. in the presence of steam followed by rapid cooling, thereby “cracking” large hydrocarbons into smaller ones and introducing unsaturation. Ethylene may then be separated from the resulting product mixture by repeated compression and distillation processes. Common drawbacks of the steam-cracking processes can include environmental issues, like CO2 and NOx production, and its energy-intensive nature, which results in a high-cost process. Further, alternative methods used in place of steam-cracking, including fluidized bed catalytic process, have their own limitations and drawbacks.
Other methods are known for producing alkenes, e.g., acid dehydration of alcohols. Generally, acid dehydration of alcohols proceeds by reaction of alkyl halides and metal hydroxides. Such methods, however, have heretofore, not been commercially viable. The primary hindrances to commercial scale-up of these methods include catalyst attrition and over-halogenation problems, which result in the need for expensive re-crystallation.
Among other things, a need remains unaddressed for a process to form alkenes in commercially viable processes, with a minimization or elimination of undesirable byproducts including higher halides.